This application claims priority to the Switzerland Patent Application No. 0830/01, filed May 8, 2001,which application is hereby incorporated in its entirety.
1. Field of the Invention
The invention relates to a workpiece support for a coating unit, in particular a workpiece support for use in a vacuum coating unit. A workpiece support of this type usually carries a relatively large number of workpieces, in a manner such that, in order to ensure uniform coating, they move past coating sources, in a composite movement produced, for example, by superposition of a plurality of elemental movements, generally circular movements, and simultaneously rotate.
2. Prior Art
Workpiece supports in which the drivers are each mounted on a rod parallel to the shaft and passing through adjacent to the turntables are known. This has the disadvantage that, if the distances between the turntables are changed for adaptation to the length of the workpieces, the drivers must be correspondingly displaced and have to be readjusted, which entails considerable effort and in particular requires several test runs. If a turntable is changed, the driver too has to be changed or at least readjusted. An incorrect adjustment can have serious consequences.
A solution similar in design to the known solution of the generic type, in which, however, the possibility of changing the distances between the turntables or of replacing turntables is not provided, is described, for example in DE-A-198 03 278. WO-A-00/36 178 describes, inter alia, a workpiece support of the generic type, in which a driver is coordinated with each turntable and is rotatably supported on the upper surface of said turntable. However, the driver is not firmly connected to the turntable, so that, as a rule, it has to be remounted and readjusted in the case of changes to the workpiece support.
It is the object of the invention to provide a workpiece support of the generic type, in which adaptations to the respective workpiece geometries and to other requirements with respect to the coating process, for example by changes of the distances between the turntables or by replacement of the turntables, are possible readily and without considerable effort.
The present invention is directed to a workpiece support unit for a coating unit. In one embodiment, the workpiece support unit has at least one drivable shaft rotatable about a main axis of rotation, a plurality of turntables that are non-rotatably connected to the shaft, at least one workpiece holder, a plurality of driving devices, and a stop. Each driving device is mounted to one respective turntable so as to be rotatable about the main axis of rotation and to be non-displaceable in the axial direction of the shaft. Each driving device includes a driver that is coordinated with the turntable so that it engages at least intermittently with at least one workpiece holder, which is rotatably mounted onto the turntable, to cause the workpiece holder to rotate about its axis of rotation. Finally, the stop cooperates with a portion of each driving device to limit the rotation of the driving device.
The advantages achieved by the invention are in particular that the respective driver need be adjusted only once. In particular, changes to the distances between the turntables or the replacement of individual turntables do not necessitate any readjustment. Even the single adjustment can be carried out on the individual turntable without other components of the unit having to be included. Turntables formed according to the invention can generally readily be integrated into existing coating units.
The invention permits assembly of the workpiece support from individual building blocks, in particular from turntables forming in each case a compact and robust unit, which can be assembled according to the modular principle and, apart from the force-transmitting shaft/turntable fit and a similar external diameter of the turntables, need not be particularly tailored to one another. For example, the turntables can thus be formed differently without requiring adaptations of other parts of the unit.
In particular, turntables of different designs can simultaneously be used on one and the same workpiece support. They can be provided with different pitches, i.e. different numbers of workpiece holders, for example in adaptation to the respective workpiece geometry or can be formed in adaptation to specific requirements relating to the coating of the workpieces arranged on them, for example for intermittent or continuous rotation of the workpiece. It is also possible for turntables formed according to the invention and those formed conventionally to be combined in a workpiece support.
In any case, the driving device can be mounted completely or predominantly outside the trajectory of the workpiece and the driver can engage with the workpiece holders from the edge of the turntable so that components interfering with the coating process and overlapping the workpieces are not required. At the same time, however, the driving device can be compactly formed and arranged so that turntables formed according to the invention have the same or only a slightly larger height in comparison with conventional turntables.